While attending the funeral for Amber, Homer's now dead Vegas wife, Bart gets bored and plays a game of paddle ball, which goes awry by everyone getting choked by the paddle ball. As a result, he is forced to see a therapist who suggests Bart get a drum kit. Bart gets a kit and instantly becomes a natural at it in seconds, as he starts hallucinating Homer's face in every drum and cymbal sometimes. He practices non-stop, and bumps into The White Stripes who are playing "The Hardest Button to Button" in a parody of its Michael Gondry-directed video. Eventually, his drumming drives Homer and Marge mad and Lisa suggests to her parents that she can take Bart to a jazz brunch.

Lisa asks Bart to jazz along with her quintet at Jazzy Goodtime's, which he does. Bart easily overshadows everyone, including Lisa, and a legendary jazz group asks him to play with them, much to Lisa's chagrin.

Bart's drumming is such a success that he's a town icon and made the front cover of two magazines, thus making Lisa very annoyed as she knows Bart is not worthy of his newfound popularity. Marge, who doesn't want Lisa to compete against Bart, chooses to let her adopt a puppy in order to make her happy. At the animal shelter, Lisa picks the cutest puppy over a very sick dog that would otherwise die. At night, the sick dog comes in a ghost-like form to tell her that his fate is doomed because she chose the other dog over him. Lisa plans to go back and adopt the sick puppy, but after seeing how sick many of them are, she chooses to adopt them all in order to save their lives. On her way home, many other animals join her, including a horde of circus animals. Having nowhere to put them, Lisa places them in the attic.

After dinner that night, Lisa goes into the attic and finds Bart jazzing with the animals she rescued. A tiger bites Bart's "drumming arm" causing extensive nerve damage and meaning that he can no longer play.

In order to raise money for the operation he needs, Bart organizes a benefit concert with his Jazz friends. Meanwhile, Lisa is informed that her animals will be taken to a pound and killed if she is unable find a suitable home for them. In the end, after the benefit concert was a good success, Bart feels empathy for Lisa and plans to use the money to build a home for all the animals.